How much air could a dinosaur breathe?

Early dinosaurs got tuckered out faster than Tyrannosaurus rex and other species living near the end of the dinosaurs' reign, according to a researcher who studies fossil ribs

The joint between an animal's backbone and its ribs provides evidence of how much the chest could expand during breathing, says Richard A. Hengst of Purdue University North Central in Westville, Ind. Hengst analyzed the ribs of 12 carnivorous dinosaur species to trace the evolution of their lung capacity--an indirect measure of aerobic endurance. The oldest species had only a limited ability to expand their chests, whereas later ones could take in 40 percent more air per breath. Hengst reported this month in Chicago at a meeting of the Society of Vertebrate Paleontology.

Dinosaurs in North America developed the improved lung capacity during the middle Jurassic period, roughly 140 million years ago. Species in South America acquired this innovation much later than their northern cousins, suggesting that they may have used different strategies in hunting. Northern species may have patrolled larger areas and run their prey down over longer distances, suggests Hengst.

John A. Ruben, a physiologist at Oregon State University in Corvallis, says that Hengst's findings make sense. "It quite independently lends some validity to work we're doing."